Oostzee (Dutch) comes from Dutch zee, from Middle Dutch sêe, from Old Dutch sēo, from Proto-West Germanic saiwi, from Proto-Germanic saiwiz, from Proto-Germanic sīhwaną, from Proto-Indo-European seykʷ-, from Proto-Indo-European sey- — to be wet; dribble; run; to stretch one's arm;...
Ancestry of “Oostzee”, step by step
Oostzee traces back through two separate lines of ancestry.